"""
NC78 反转链表
https://www.nowcoder.com/practice/75e878df47f24fdc9dc3e400ec6058ca?tpId=117&&tqId=37777&&companyId=239&rp=1&ru=/company/home/code/239&qru=/ta/job-code-high/question-ranking
"""


class ListNode:
    def __init__(self, x):
        self.val = x
        self.next = None

# 代码中的类名、方法名、参数名已经指定，请勿修改，直接返回方法规定的值即可
#
#
# @param head ListNode类
# @return ListNode类
#


class Solution:
    def ReverseList(self, head: ListNode) -> ListNode:
        # write code here
        if not head:
            return

        pre = None
        cur = head
        while cur:
            next = cur.next
            cur.next = pre
            pre = cur
            cur = next

        return pre
